Fluid-filled elastic mount having vacuum-receiving chamber partially defined by elastic member for isolating high-frequency vibrations

Abstract

A fluid-filled elastic mount including first and second support members and an elastic body interposed between these members for elastic connection thereof. The elastic mount has a pressure-receiving chamber partially defined by the elastic body, first and second equilibrium chambers defined by first and second flexible diaphragms and communicating with the pressure-receiving chamber through first and second orifice passages, respectively. The second orifice passage has a higher ratio of the cross sectional area to the length than the first orifice passage. The present elastic mount further includes an elastic restriction member which is opposed to the second diaphragm and cooperates with the diaphragm to define a vacuum-receiving chamber for allowing elastic deformation of the second diaphragm. In operation, a vacuum pressure is applied where appropriate to the vacuum-receiving chamber, to draw the second diaphragm onto the elastic restriction member, so as to restrict free deformation of the second diaphragm and permit oscillation of the diaphragm with the elastic restriction member.

What is claimed is: 
     
       1. A fluid-filled elastic mount for flexibly connecting two members, comprising: a first support member and a second support member which are respectively fixed to the two members to be flexibly connected, and which are spaced apart form each other in a load-receiving direction in which vibrations are applied to the elastic mount;   an elastic body interposed between said first and second support members for elastically connecting the first and second support members;   said elastic body at least partially defining a pressure-receiving chamber which is filled with a non-compressible fluid, a pressure of said fluid in said pressure-receiving chamber changing due to elastic deformation of said elastic body upon application of the vibrations in said load-receiving direction;   a first flexible diaphragm partially defining a first equilibrium chamber filled with said non-compressible fluid, said first flexible diaphragm being elastically deformable so as to permit a volumetric change of said first equilibrium chamber to absorb a pressure change of said fluid in said first equilibrium chamber;   means for defining a first orifice passage which communicates with said pressure-receiving chamber and said first equilibrium chamber so as to permit flow of said fluid therebetween;   a second flexible diaphragm partially defining a second equilibrium chamber filled with said non-compressible fluid, said second flexible diaphragm being elastically deformable so as to permit a volumetric change of said second equilibrium chamber to absorb a pressure change of said fluid in said second equilibrium chamber;   a fixed partition plate separating said pressure-receiving chamber and said second equilibrium chamber;   means for defining a second orifice passage through said fixed partition plate so as to permit flow of said fluid between said pressure-receiving chamber and said second equilibrium chamber, said second orifice passage having a ratio of a cross sectional area thereof to a length thereof, which ratio is higher than that of said first orifice passage;   a movable elastic restriction member which is opposed to said second flexible diaphragm to at least partially define an air-tight vacuum-receiving chamber, such that said second equilibrium chamber is separated from said vacuum-receiving chamber only by said second flexible diaphragm, said vacuum-receiving chamber permitting elastic deformation of said second flexible diaphragm; and   pressure control means for selectively applying a vacuum pressure to said vacuum-receiving chamber to draw said second flexible diaphragm onto said elastic restriction member, so as to restrict free deformation of said second flexible diaphragm and permit oscillation of the second flexible diaphragm with said elastic restriction member.   
     
     
       2. A fluid-filled elastic mount according to claim 1, wherein said means for defining a first orifice passage and said means for defining a second orifice passage comprise a partition structure, including said fixed partition plate, supported by said second support member, said pressure-receiving chamber being formed on one of opposite sides of said partition structure on the side of said first support member, said partition structure cooperating with said second support member to define an enclosed space on the other side of the partition structure. 
     
     
       3. A fluid-filled elastic mount according to claim 2, wherein said elastic restriction member is supported by said partition structure to divide said enclosed space into a first section formed between said elastic restriction member and said second support member, and a second section formed between said elastic restriction member and said partition structure, said first section being divided by s id first flexible diaphragm into said first equilibrium chamber and an air chamber, said second section being divided by said second flexible diaphragm into said second equilibrium chamber and said vacuum-receiving chamber. 
     
     
       4. A fluid-filled elastic mount according to claim 3, wherein said elastic restriction member is a disc-like rubber membrane which is secured at an outer circumferential surface to said partition structure. 
     
     
       5. A fluid-filled elastic mount according to claim 3, further comprising a rigid stopper member supported by said partition structure and partially defining said first equilibrium chamber, said stopper member being opposed to said elastic restriction member, for restricting elastic deformation of said elastic restriction member. 
     
     
       6. A fluid-filled elastic mount according to claim 3, wherein said partition structure defines an air passage communicating with said vacuum-receiving chamber, said pressure control means comprising an air conduit connected to said air passage for applying said vacuum pressure to said vacuum-receiving chamber. 
     
     
       7. A fluid-filled elastic mount according to claim 1, wherein said pressure control means comprises switching means which is operable between a first position for applying a pressure not lower than an atmospheric pressure to said vacuum-receiving chamber, and a second position for applying said vacuum pressure to said vacuum-receiving chamber, said non-compressible fluid flowing substantially exclusively through said second orifice passage when said switching means is placed in said first position, and through said first orifice passage when said switching means is placed in said second position. 
     
     
       8. A fluid-filled elastic mount according to claim 7, wherein said pressure control means further comprises a vacuum pressure source for supplying said vacuum-receiving chamber with said vacuum pressure when said switching means is placed in said second position, said vacuum-receiving chamber being held in communication with the atmosphere having the atmospheric pressure when said switching means is placed in said first position. 
     
     
       9. A fluid-filled elastic mount according to claim 1, wherein said pressure control means is connected to an intake pipe of an engine of a motor vehicle as a source of said vacuum pressure to be applied to said vacuum-receiving chamber.